This invention relates to an apparatus and method for installing and setting an annular seal between the casing hanger and wellhead housing in an oil and gas well. The increased use of metal-to-metal sealing means for these wellhead annulus seals has created a need for means for generating the large loads needed to energize these seals. The blowout preventers typically positioned immediately above the wellhead housing are designed to seal against and withstand the high well bore pressures found in drilling operations. It has been proposed to use this capacity to activate a metal-to-metal seal. This technique has posed problems such as how to isolate the seal setting procedure to avoid pressurizing the formation, requiring the use of tools which must be sealed against the well bore drilling fluids to function properly, and using tools which require rotation of the drill pipe handling string while the blowout preventers are closed on the handling string.
This invention is for a wellhead seal and casing hanger installation tool which utilizes the hydraulic force available when the blowout preventers are sealed against a purpose built drill pipe sub and pressurized fluid is supplied through the kill and choke lines to the annulus between the drill pipe sub and the blowout preventer body. Fluid passages in the wall of the drill pipe sub direct the pressurized fluid to a hydraulically actuable piston which energizes and latches the wellhead annulus packoff. This eliminates the need for additional flow controlling means as ball valves or darts inserted in the drill pipe. The tool allows installation of the casing hanger and wellhead annulus packoff in a single trip while utilizing the aforementioned hydraulic force to simplify the seal setting procedure. The tool is particularly suited for use with metal-to-metal seals which often require high axial forces to initiate the seal.
Prior casing hanger and packoff installation tools include the M. R. Jones U.S. Pat. No. 3,093,996 which discloses a blowout preventer tester which lands in the wellhead housing and uses a floating piston as a medium separator to allow drilling fluids to be pumped down the drill pipe to pressurize inert gas injected into the blowout preventer body for testing purposes. The gas is injected through a valve and porting means in the blowout preventer body.
The C. C. Brown U.S. Pat. No. 3,279,539 shows a seal setting tool using a piston to activate a seal assembly. The tool requires a ball to be dropped down the drill pipe, and pressurizing the drill pipe to shift the piston and energize the seal.
The C. C. Brown U.S. Pat. No. 3,357,486 discloses another seal setting structure which allows for either mechanical or hydraulic actuation of the seal assembly. The Brown invention requires the seal setting structure to be aligned with a groove in the wellhead housing for proper orientation and operation.
The J. A. Haeber U.S. Pat. No. 3,543,847 discloses a seal installation tool which uses the weight of the drill string to initially set the seal and BOP test pressure to apply additional actuation load and activate a lockdown mechanism into an annular groove in the wellhead housing interior.
The A. G. Ahlstone U.S. Pat. No. 3,897,823 discloses a similar structure which utilizes a combination of drill string weight and hydraulic force to set the seal and uses a wedge-type lock against the interior wall of the wellhead housing.
The E. Thuse U.S. Pat. No. 4,019,579 and the M. E. Garrett U.S. Pat. No. 4,019,580 disclose an apparatus for installing a wellhead annulus packoff which includes a piston operated by hydraulic pressure supplied through the drill string and a nut and screw arrangement which converts the piston's linear movement into torque for energizing the packoff.